End-functionalized π-conjugated polymers are highly desirable for the creation of multifunctional polymers or hybrid materials such as rod-b-coil diblock copolymers, donor-acceptor diblock copolymers and surface-modified inorganic materials for organic photovoltaics. In order to prepare polymer chains bearing one or two end-functionalized groups, the following four approaches can be envisaged: (i) post-functionalization of a purified polymer; (ii) use of a functionalized initiator agent; (iii) termination reaction with functionalized quenching reagent using the same metal catalyst as the polymerization; and (iv) combination of initiator and quenching reagents (combining approaches (ii) and (iii)). The advantage of the first approach (i) is the selective functionalization of either the α- or ω-end, as well as both ends. However, there are some drawbacks with approach (i) in that two separate reactions for polymerization and end-functionalization are required. Also, in some cases, post-modification requires low-temperature conditions involving lithiation procedures, which can promote the aggregation of π-conjugated polymers in the reaction solution. Approaches (ii) and (iii) are effective for introducing one end-group on the polymer in a one-pot reaction. In comparison with the other approaches, approach (iv) has been relatively less investigated; the use of Suzuki-Miyaura coupling-based polymerizations to achieve both α- and ω-end-functionalization. In almost every approach mentioned above, C—C bond formation was used for end-functionalization. Reports concerning carbon-heteroatom end-functionalization are very limited and only C—P and C—Sn bond formation to produce end-functionalized poly(3-hexylthiophenes) (P3HTs) have been reported where approach (i) was used.
Thiol-functionalized polymers are useful for forming self-assembled monolayers (SAMs) on surfaces, and for the thiol click reaction for constructing multi-functionalized materials via thioester linkages. However, thiol end-capped π-conjugated polymers have not undergone full synthetic investigations nor physical property studies.
Despite the advances in the development of synthetic methods for making thiol-end-capped π-conjugated polymers, a need exist for methods for making specifically end-capped polymers. The present invention seeks to fulfill this need and provides further related advantages.